notebook: make sure to reset to zero tab borders for gedit and ephy
notebook: make sure to reset to zero tab borders for gedit and ephy

Since we override the notebook border for those applications, we also
make sure to reset to zero the notebook tab region border, or we get bad
drawing artifacts.

rgcjonas/adwaita-semidark,cosimoc/gnome-themes-standard,Distrotech/gnome-themes-standard,ChrisCummins/gnome-themes-standard,magcius/gnome-themes-standard,DoctorJellyface/gnome-themes-standard,cosimoc/gnome-themes-standard,ChrisCummins/gnome-themes-standard,rgcjonas/adwaita-semidark,rgcjonas/adwaita-semidark,cosimoc/gnome-themes-standard,magcius/gnome-themes-standard,cosimoc/gnome-themes-standard,magcius/gnome-themes-standard,ChrisCummins/gnome-themes-standard,DoctorJellyface/gnome-themes-standard,Distrotech/gnome-themes-standard,ChrisCummins/gnome-themes-standard,rgcjonas/adwaita-semidark,ChrisCummins/gnome-themes-standard